revwalk: add test hiding a commit without a merge base

Nothing should be hidden and this shouldn't bother the merge base
calculation.

tests-clar/revwalk/basic.c

@@ -163,3 +163,19 @@ void test_revwalk_basic__push_head_hide_ref(void)
 	/* git log HEAD --oneline --not refs/heads/packed-test | wc -l => 4 */
 	cl_assert(i == 4);
 }
+
+void test_revwalk_basic__push_head_hide_ref_nobase(void)
+{
+	int i = 0;
+	git_oid oid;
+
+	cl_git_pass(git_revwalk_push_head(_walk));
+	cl_git_pass(git_revwalk_hide_ref(_walk, "refs/heads/packed"));
+
+	while (git_revwalk_next(&oid, _walk) == GIT_SUCCESS) {
+		i++;
+	}
+
+	/* git log HEAD --oneline --not refs/heads/packed | wc -l => 7 */
+	cl_assert(i == 7);
+}